DIVERSE CARDIOPROTECTIVE SIGNALING MECHANISMS OF PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR-γ LIGANDS, 15-DEOXY-Δ12,14-PROSTAGLANDIN J2 AND CIGLITAZONE, IN REPERFUSION INJURY

Enhanced cardioprotective activity of ferulic acid-loaded solid lipid nanoparticle in an animal model of myocardial injury

Myocardial infarction results in an increased inflammatory and oxidative stress response in the heart, and reducing inflammation and oxidative stress after MI may offer protective effects to the heart. In the present study, we examined the cardioprotective effects of ferulic acid (FA) and ferulic acid nanostructured solid lipid nanoparticles (FA-SLNs) in an isoproterenol (ISO) induced MI model. Male Sprague Dawley rats were divided into five experimental groups to compare the effects of FA and FA-SLNs. The findings revealed that ISO led to extensive cardiomyopathy, characterized by increased infarction area, edema formation, pressure load, and energy deprivation. Additionally, ISO increased the levels of inflammatory markers (COX-2, NLRP3, and NF-кB) and apoptotic mediators such as p-JNK. However, treatment with FA and FA-SLNs mitigated the severity of the ISO-induced response, and elevated the levels of antioxidant enzymes while downregulating inflammatory pathways, along with upregulation of the mitochondrial bioenergetic factor PPAR-γ. Furthermore, virtual docking analysis of FA with various protein targets supported the in vivo results, confirming drug-protein interactions. Overall, the results demonstrated that FA-SLNs offer a promising strategy for protecting the heart from further injury following MI. This is attributed to the improved drug delivery and therapeutic outcomes compared to FA alone.

Untangling the Cooperative Role of Nuclear Receptors in Cardiovascular Physiology and Disease

The heart is the first organ to acquire its physiological function during development, enabling it to supply the organism with oxygen and nutrients. Given this early commitment, cardiomyocytes were traditionally considered transcriptionally stable cells fully committed to contractile function. However, growing evidence suggests that the maintenance of cardiac function in health and disease depends on transcriptional and epigenetic regulation. Several studies have revealed that the complex transcriptional alterations underlying cardiovascular disease (CVD) manifestations such as myocardial infarction and hypertrophy is mediated by cardiac retinoid X receptors (RXR) and their partners. RXRs are members of the nuclear receptor (NR) superfamily of ligand-activated transcription factors and drive essential biological processes such as ion handling, mitochondrial biogenesis, and glucose and lipid metabolism. RXRs are thus attractive molecular targets for the development of effective pharmacological strategies for CVD treatment and prevention. In this review, we summarize current knowledge of RXR partnership biology in cardiac homeostasis and disease, providing an up-to-date view of the molecular mechanisms and cellular pathways that sustain cardiomyocyte physiology.

Rethinking pioglitazone as a cardioprotective agent: a new perspective on an overlooked drug

Since 1985, the thiazolidinedione pioglitazone has been widely used as an insulin sensitizer drug for type 2 diabetes mellitus (T2DM). Although fluid retention was early recognized as a safety concern, data from clinical trials have not provided conclusive evidence for a benefit or a harm on cardiac function, leaving the question unanswered. We reviewed the available evidence encompassing both in vitro and in vivo studies in tissues, isolated organs, animals and humans, including the evidence generated by major clinical trials. Despite the increased risk of hospitalization for heart failure due to fluid retention, pioglitazone is consistently associated with reduced risk of myocardial infarction and ischemic stroke both in primary and secondary prevention, without any proven direct harm on the myocardium. Moreover, it reduces atherosclerosis progression, in-stent restenosis after coronary stent implantation, progression rate from persistent to permanent atrial fibrillation, and reablation rate in diabetic patients with paroxysmal atrial fibrillation after catheter ablation. In fact, human and animal studies consistently report direct beneficial effects on cardiomyocytes electrophysiology, energetic metabolism, ischemia–reperfusion injury, cardiac remodeling, neurohormonal activation, pulmonary circulation and biventricular systo-diastolic functions. The mechanisms involved may rely either on anti-remodeling properties (endothelium protective, inflammation-modulating, anti-proliferative and anti-fibrotic properties) and/or on metabolic (adipose tissue metabolism, increased HDL cholesterol) and neurohormonal (renin–angiotensin–aldosterone system, sympathetic nervous system, and adiponectin) modulation of the cardiovascular system. With appropriate prescription and titration, pioglitazone remains a useful tool in the arsenal of the clinical diabetologist.

Dimethyl Itaconate-Loaded Nanofibers Rewrite Macrophage Polarization, Reduce Inflammation, and Enhance Repair of Myocardic Infarction

Cellular metabolism plays a major role in the regulation of inflammation. The inflammatory macrophages undergo a wide-range of metabolic rewriting due to the production of significant amount of itaconate metabolite from cis-aconitate in the tricarboxylic acid cycle. This itaconate molecule has been recently described as a promising immunoregulator. However, its function and mode of action on macrophages and tissue repair and regeneration are yet unclear. Herein, the itaconate-derivative dimethyl itaconate (DMI) suppresses the IL-23/IL-17 inflammatory axis-associated genes and promotes antioxidant nuclear factor erythroid 2-related factor 2 target genes. The poly-ε-caprolactone (PCL)/DMI nanofibers implanted in mice initially maintain inflammation by suppressing anti-inflammatory activity and particular inflammation, while at later stage promotes anti-inflammatory activity for an appropriate tissue repair. Furthermore, the PCL/DMI nanofiber patches show an excellent myocardial protection by reducing infarct area and improving ventricular function via time-dependent regulation of myocardium-associated genes. This study unveils potential DMI macrophage modulatory functions in tissue microenvironment and macrophages rewriting for proper tissue repair.

Morin reduces inflammatory responses and alleviates lipid accumulation in hepatocytes

Morin (MO), a natural bioflavinoid, exists in many herbs. Previous studies have acclaimed MO's anti-inflammatory, antidiabetic, antioxidant, antifibrotic, anticancer, and antihyperglycemic biological effects. This study aimed to assess the molecular mechanism of MO involved in the oleic acid (OA)-induced inflammatory damage and lipid accumulation in HepG2 cell and tyloxapol (Ty)-induced hyperlipidemia in mice. We found that MO can efficaciously mitigate reactive tumor necrosis factor-α (TNF-α) level and triglyceride (TG) accumulation in OA-induced HepG2 cell and in tyloxapol-induced mice. Next, the study testified that MO apparently suppressed OA-excited nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs) signaling pathways in HepG2 cell. In addition, MO distinctly upregulated the expression of peroxisome proliferator-activated receptor α (PPARα) and decreased the expression of sterol regulatory element-binding protein 1c (SREBP-1c) in OA-induced HepG2 cell and in tyloxapol-induced mice, both of which are dependent upon the phosphorylation of acetyl-CoA carboxylase (ACC), adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK), and protein kinase B (AKT). In conclusion, these results suggest that MO has protective potential against hyperlipidemia and steatosis, and the potential mechanism may have a close relation with activation of PPARα and inhibition of SREBP-1c.

CRTH2 promotes endoplasmic reticulum stress-induced cardiomyocyte apoptosis through m-calpain

Apoptotic death of cardiac myocytes is associated with ischemic heart disease and chemotherapy‐induced cardiomyopathy. Chemoattractant receptor‐homologous molecule expressed on T helper type 2 cells (CRTH2) is highly expressed in the heart. However, its specific role in ischemic cardiomyopathy is not fully understood. Here, we demonstrated that CRTH2 disruption markedly improved cardiac recovery in mice postmyocardial infarction and doxorubicin challenge by suppressing cardiomyocyte apoptosis. Mechanistically, CRTH2 activation specifically facilitated endoplasmic reticulum (ER) stress‐induced cardiomyocyte apoptosis via caspase‐12‐dependent pathway. Blockage of m‐calpain prevented CRTH2‐mediated cardiomyocyte apoptosis under ER stress by suppressing caspase‐12 activity. CRTH2 was coupled with G_αq to elicit intracellular Ca²⁺ flux and activated m‐calpain/caspase‐12 cascade in cardiomyocytes. Knockdown of caspase‐4, an alternative to caspase‐12 in humans, markedly alleviated CRHT2 activation‐induced apoptosis in human cardiomyocyte response to anoxia. Our findings revealed an unexpected role of CRTH2 in promoting ER stress‐induced cardiomyocyte apoptosis, suggesting that CRTH2 inhibition has therapeutic potential for ischemic cardiomyopathy.

Effect of Hexadecyl Azelaoyl Phosphatidylcholine on Cardiomyocyte Apoptosis in Myocardial Ischemia-Reperfusion Injury: A Hypothesis

Reperfusion after myocardial ischemia can induce cardiomyocyte death, known as myocardial reperfusion injury. The pathophysiology of the process of reperfusion suggests the confluence multiple pathways. Recent studies have focused on the inflammatory response, which is considered to be the main mechanism during the process of myocardial ischemia-reperfusion injury and can cause cardiomyocyte apoptosis. Peroxisome proliferator-activated receptors gamma activated by endogenous ligands and exogenous ligand can decrease the inflammatory response in cardiomyocytes. Thiazolidinediones are synthetic, high-affinity, selective ligands for peroxisome proliferator-activated receptors gamma, and can inhibit the inflammatory response, decrease myocardial infarct size, and protect cardiac function. However, thiazolidinediones, including rosiglitazone and pioglitazone, can also contribute to adverse cardiovascular events such as congestive heart failure. Therefore, there are some limitations to the use of thiazolidinediones. Most endogenous ligands were of low affinity until hexadecyl azelaoyl phosphatidylcholine was identified as a high-affinity ligand and agonist for peroxisome proliferator-activated receptors gamma. Hexadecyl azelaoyl phosphatidylcholine binds recombinant peroxisome proliferator-activated receptors with an affinity (Kd(app) ≈40 nM) which is equivalent to rosiglitazone. Therefore, hexadecyl azelaoyl phosphatidylcholine is a specific peroxisome proliferator-activated receptors gamma agonist. Given these findings, we hypothesized that the use of hexadecyl azelaoyl phosphatidylcholine can activate the peroxisome proliferator-activated receptors gamma signal pathways and prevent the inflammatory response process of myocardial ischemia-reperfusion injury, with reduced cardiomyocyte apoptosis and death.

Mechanism underlying methyl eugenol attenuation of intestinal ischemia/reperfusion injury

Intestinal ischemia/reperfusion (I/R) injury is associated with a high risk of mortality in the clinical situation. Many factors are involved in I/R, including reactive oxygen species, cytokine release, and apoptosis. We aimed to determine whether a pure methyl eugenol (ME) given before intestinal ischemia, protects against intestinal I/R injury and the possible mechanism involved in this protection. Rat received ME (100 mg/kg) for 30 days then underwent intestinal I/R with 30 min ischemia and 60 min reperfusion. Serum lactate dehydrogenase (LDH) level, tissue malondialdehyde (MDA), as well as some antioxidant biomarkers were assessed, while the serum level of tumor necrosis factor alpha (TNF-α) was determined by ELISA. The change in TNF-α and interleukin 6 (IL-6) gene expressions were evaluated and confirmed by assessing protein level of TNF-α in the intestinal tissue by immunohistochemistry. Apoptosis was evaluated using DNA-laddering assay and by detecting caspase-3 immunohistochemically. Administration of ME prior to I/R injury resulted in a modulation of the production of MDA, LDH, and nitric oxide and restoration of the tested oxidative stress biomarkers. Pretreatment with ME downregulated messenger RNA of TNF-α and IL-6 inflammatory cytokines and their protein expressions in I/R rats. Marked inhibition of the apoptotic DNA and improvement of the architectures of small intestine were observed after pretreatment with ME. ME exhibits a protective effect against intestinal I/R via amelioration of the oxidative stress and inflammatory cytokines gene expression. Therefore, the supplementation of ME prior to intestinal I/R might be helpful in the attenuation of I/R complications.

Hydrogen Sulfide Confers Lung Protection During Mechanical Ventilation via Cyclooxygenase 2, 15-deoxy Δ12,14-Prostaglandin J2, and Peroxisome Proliferator-Activated Receptor Gamma

OBJECTIVES

Hydrogen sulfide reduces ventilator-induced lung injury in mice. Here, we have examined the underlying mechanisms of hydrogen sulfide-mediated lung protection and determined the involvement of cyclooxygenase 2, 15-deoxy Δ-prostaglandin J2, and peroxisome proliferator-activated receptor gamma in this response.

DESIGN

Randomized, experimental study.

SETTING

University medical center research laboratory.

SUBJECTS

C57BL/6 mice and in vitro cell catheters.

INTERVENTIONS

The effects of hydrogen sulfide were analyzed in a mouse ventilator-induced lung injury model in vivo as well as in a cell stretch model in vitro in the absence or presence of hydrogen sulfide. The physiologic relevance of our findings was confirmed using pharmacologic inhibitors of cyclooxygenase 2 and peroxisome proliferator-activated receptor gamma.

MEASUREMENTS AND MAIN RESULTS

Mechanical ventilation caused significant lung inflammation and injury that was prevented in the presence of hydrogen sulfide. Hydrogen sulfide-mediated protection was associated with induction of cyclooxygenase 2 and increases of its product 15-deoxy Δ-prostaglandin J2 as well as cyclooxygenase 2/15-deoxy Δ-prostaglandin J2-dependent activation of peroxisome proliferator-activated receptor gamma. Hydrogen sulfide-dependent effects were mainly observed in macrophages. Applied mechanical stretch to RAW 264.7 macrophages resulted in increased expression of interleukin receptor 1 messenger RNA and release of macrophage inflammatory protein-2. In contrast, incubation of stretched macrophages with sodium hydrosulfide prevented the inflammatory response dependent on peroxisome proliferator-activated receptor gamma activity. Finally, application of a specific peroxisome proliferator-activated receptor gamma inhibitor abolished hydrogen sulfide-mediated protection in ventilated animals.

CONCLUSIONS

One hydrogen sulfide-triggered mechanism in the protection against ventilator-induced lung injury involves cyclooxygenase 2/15-deoxy Δ-prostaglandin J2-dependent activation of peroxisome proliferator-activated receptor gamma and macrophage activity.

Transient Receptor Potential Ankyrin 1 Activation within the Cardiac Myocyte Limits Ischemia-reperfusion Injury in Rodents

BACKGROUND

Recent evidence suggests that cross talk exists between cellular pathways important for pain signaling and ischemia-reperfusion injury. Here, the authors address whether the transient receptor potential ankyrin 1 (TRPA1) channel, important in pain signaling, is present in cardiac myocytes and regulates cardiac ischemia-reperfusion injury.

METHODS

For biochemical analysis of TRPA1, techniques including quantitative polymerase chain reaction, Western blot, and immunofluorescence were used. To determine how TRPA1 mediates cellular injury, the authors used an in vivo model of rat cardiac ischemia-reperfusion injury and adult rat-isolated cardiac myocytes subjected to hypoxia-reoxygenation.

RESULTS

The authors' biochemical analysis indicates that TRPA1 is within the cardiac myocytes. Further, using a rat in vivo model of cardiac injury, the TRPA1 activators ASP 7663 and optovin reduce myocardial injury (45 ± 5%* and 44 ± 8%,* respectively, vs. control, 66 ± 6% infarct size/area at risk; n = 6 per group; mean ± SD; *P < 0.001). TRPA1 inhibition also blocked the infarct size-sparing effects of morphine. In isolated cardiac myocytes, the TRPA1 activators ASP 7663 and optovin reduce cardiac myocyte cell death when given during reoxygenation (20 ± 3%* and 22 ± 4%* vs. 36 ± 3%; percentage of dead cells per field, n = 6 per group; mean ± SD; *P < 0.05). For a rat in vivo model of cardiac injury, the infarct size-sparing effect of TRPA1 activators also occurs during reperfusion.

CONCLUSIONS

The authors' data suggest that TRPA1 is present within the cardiac myocytes and is important in regulating myocardial reperfusion injury. The presence of TRPA1 within the cardiac myocytes may potentially explain why certain pain relievers that can block TRPA1 activation, such as cyclooxygenase-2 inhibitors or some nonsteroidal antiinflammatory drugs, could be associated with cardiovascular risk.

The Role of Peroxisome Proliferator-Activated Receptor γ in Mediating Cardioprotection Against Ischemia/Reperfusion Injury

Myocardial infarction (MI) is a serious cardiovascular disease resulting in high rates of morbidity and mortality. Although advances have been made in restoring myocardial perfusion in ischemic areas, decreases in cardiomyocyte death and infarct size are still limited, attributing to myocardial ischemia/reperfusion (I/R) injury. It is necessary to develop therapies to restrict myocardial I/R injury and protect cardiomyocytes against further damage after MI. Many studies have suggested that peroxisome proliferator-activated receptor γ (PPARγ), a ligand-inducible nuclear receptor that predominantly regulates glucose and lipid metabolism, is a promising therapeutic target for ameliorating myocardial I/R injury. Thus, this review focuses on the role of PPARγ in cardioprotection during myocardial I/R. The cardioprotective effects of PPARγ, including attenuating oxidative stress, inhibiting inflammatory responses, improving glucose and lipid metabolism, and antagonizing apoptosis, are described. Additionally, the underlying mechanisms of cardioprotective effects of PPARγ, such as regulating the expression of target genes, influencing other transcription factors, and modulating kinase signaling pathways, are further discussed.

PPARγ and Its Role in Cardiovascular Diseases

Peroxisome proliferator-activated receptor Gamma (PPARγ), a ligand-activated transcription factor, has a role in various cellular functions as well as glucose homeostasis, lipid metabolism, and prevention of oxidative stress. The activators of PPARγ are already widely used in the treatment of diabetes mellitus. The cardioprotective effect of PPARγ activation has been studied extensively over the years making them potential therapeutic targets in diseases associated with cardiovascular disorders. However, they are also associated with adverse cardiovascular events such as congestive heart failure and myocardial infarction. This review aims to discuss the role of PPARγ in the various cardiovascular diseases and summarize the current knowledge on PPARγ agonists from multiple clinical trials. Finally, we also review the new PPARγ agonists under development as potential therapeutics with reduced or no adverse effects.

Functional Role of Milk Fat Globule-Epidermal Growth Factor VIII in Macrophage-Mediated Inflammatory Responses and Inflammatory/Autoimmune Diseases

Inflammation involves a series of complex biological processes mediated by innate immunity for host defense against pathogen infection. Chronic inflammation is considered to be one of the major causes of serious diseases, including a number of autoimmune/inflammatory diseases, cancers, cardiovascular diseases, and neurological diseases. Milk fat globule-epidermal growth factor 8 (MFG-E8) is a secreted protein found in vertebrates and was initially discovered as a critical component of the milk fat globule. Previously, a number of studies have reported that MFG-E8 contributes to various biological functions including the phagocytic removal of damaged and apoptotic cells from tissues, the induction of VEGF-mediated neovascularization, the maintenance of intestinal epithelial homeostasis, and the promotion of mucosal healing. Recently, emerging studies have reported that MFG-E8 plays a role in inflammatory responses and inflammatory/autoimmune diseases. This review describes the characteristics of MFG-E8-mediated signaling pathways, summarizes recent findings supporting the roles of MFG-E8 in inflammatory responses and inflammatory/autoimmune diseases, and discusses MFG-E8 targeting as a potential therapeutic strategy for the development of anti-inflammatory/autoimmune disease drugs.

Endogenous Generation and Signaling Actions of Omega-3 Fatty Acid Electrophilic Derivatives

Dietary omega-3 polyunsaturated fatty acids (PUFAs) are beneficial for a number of conditions ranging from cardiovascular disease to chronic airways disorders, neurodegeneration, and cancer. Growing evidence has shown that bioactive oxygenated derivatives are responsible for transducing these salutary effects. Electrophilic oxo-derivatives of omega-3 PUFAs represent a class of oxidized derivatives that can be generated via enzymatic and nonenzymatic pathways. Inflammation and oxidative stress favor the formation of these signaling species to promote the resolution of inflammation within a fine autoregulatory loop. Endogenous generation of electrophilic oxo-derivatives of omega-3 PUFAs has been observed in in vitro and ex vivo human models and dietary supplementation of omega-3 PUFAs has been reported to increase their formation. Due to the presence of an α,β-unsaturated ketone moiety, these compounds covalently and reversibly react with nucleophilic residues on target proteins triggering the activation of cytoprotective pathways, including the Nrf2 antioxidant response, the heat shock response, and the peroxisome proliferator activated receptor γ (PPARγ) and suppressing the NF-κB proinflammatory pathway. The endogenous nature of electrophilic oxo-derivatives of omega-3 PUFAs combined with their ability to simultaneously activate multiple cytoprotective pathways has made these compounds attractive for the development of new therapies for the treatment of chronic disorders and acute events characterized by inflammation and oxidative stress.

Transcription factors Hsf1 and Nrf2 engage in crosstalk for cytoprotection

Transcription factors heat shock factor (Hsf)1 and nuclear factor-erythroid 2 p45-related factor (Nrf)2 are critical for adaptation and survival. Each is maintained at low basal levels, but is robustly activated by various stimuli, including cysteine-reactive small molecules (inducers). Although each is regulated by distinct mechanisms, it is emerging that these transcription factors engage in crosstalk by sharing overlapping transcriptional targets, such as heat shock protein (HSP)70, p62, and activating transcription factor (ATF)3, and in certain cases, compensating for each other. Critically, activation of Hsf1 or Nrf2 affects the cellular redox balance by promoting the reduced state. Conversely, deletion of Hsf1 or Nrf2 is associated with oxidative stress and impaired mitochondrial function. Transient activation of Hsf1 and Nrf2 is cytoprotective, but their persistent upregulation may be detrimental, causing cardiomyopathy or accelerating carcinogenesis, and should be considered when designing strategies for disease prevention and treatment.

Effect of peroxisome proliferator-activated receptor gamma agonist on heart of rabbits with acute myocardial ischemia/reperfusion injury

OBJECTIVE

To explore protective effect of rosiglitazone on myocardial ischemia reperfusion injury.

METHODS

A total of 48 male SD rats were randomly divided into control group (A), I/R group(B), high dose of rosiglitazone (C), low dose of rosiglitazone (D). Plasm concentration of creatine kinase (CK), CK-MB, hsCRP, Superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GSH-Px), nitric oxide (NO) and endothelin (ET) were measured 1 h later after I/R. 24 h after I/R hearts were harvested to observe pathological and ultrastructural changes. Immunohistochemistry and western blotting was used to test CD40 expression in myocardial tissue. Area of myocardial infarction were tested, arrhythmia rate during I/R was recorded.

RESULTS

Plasm concentration of creatine kinase (CK), CK-MB, hsCRP, NO, MDA and ET were decreased in group C, D compared with group B. Plasm concentration of T-SOD and GSH-Px was increased significantly in group C, D compared with group B. Compared with group B, pathological and ultrastructural changes in group C, D were slightly. Myocardial infarction area and arrhythmia rate were lower in group C, D compare with group B.

CONCLUSIONS

Rosiglitazone can protect myocardium from I/R injury by enhancing T-SOD and GSH-Px concentration, inhibit inflammatory reaction, improve endothelial function, reduce oxidative stress and calcium overload.

Conditional deletion of cardiomyocyte peroxisome proliferator-activated receptor γ enhances myocardial ischemia-reperfusion injury in mice

The nuclear transcription factor peroxisome proliferator-activated receptor γ (PPARγ) is a key regulator of the inflammatory response to an array of biologic insults. We have previously demonstrated that PPARγ ligands reduce myocardial ischemia-reperfusion injury in rodents. In the current study, we directly determined the role of cardiomyocyte PPARγ in ischemia-reperfusion injury, using a model of conditional cardiomyocyte-specific deletion of PPARγ in vivo. In mice, α-myosin heavy chain-restricted Cre-mediated PPARγ deficiency was induced by tamoxifen treatment (30 mg/kg intraperitoneally) for 4 days (PPARγ mice), whereas controls included mice treated with the oil diluent vehicle (PPARγ mice). Western blot and histochemical analyses confirmed that expression of PPARγ protein was abolished in cardiomyocytes of mice treated with tamoxifen, but not with vehicle. After tamoxifen or vehicle treatment, animals were subjected to 30-min ligation of the left anterior descending coronary artery followed by 2-h reperfusion. In PPARγ mice, myocardial ischemia and reperfusion induced extensive myocardial damage, which was associated with elevated tissue activity of myeloperoxidase, indicating infiltration of neutrophils, and elevated plasma levels of troponin I when compared with PPARγ mice. Upon echocardiographic analysis, PPARγ mice also demonstrated ventricular dilatation and systolic dysfunction. Plasma levels of the proinflammatory cytokines interleukin 1β and interleukin 6 were higher in PPARγ mice when compared with PPARγ mice. These pathological events in PPARγ mice were associated with enhanced nuclear factor κB DNA binding in the infarcted hearts. Thus, our data suggest that cardiomyocyte PPARγ is a crucial protective receptor and may prevent reperfusion injury by modulating mechanisms of inflammation.

Nitrooleate mediates nitric oxide synthase activation in endothelial cells

Nitrated lipids such as nitrooleate (OLA-NO2) can act as endogenous peroxisome proliferator-activated receptor gamma (PPARγ) ligands to exert vascular protective effects. However, the molecular mechanisms regarding nitric oxide (NO) production and its regulation are not fully defined in the vasculature. Here, we show that OLA-NO2 increased endothelial NO release by modulating activation of endothelial nitric oxide synthase (eNOS) in endothelial cells. Treatment with OLA-NO2 (3 μM) increased NO release in a time-dependent manner. OLA-NO2 decreased protein expression of eNOS and caveolin-1 (Cav-1) but increased heat shock protein 90 (Hsp90) expression. Immunoprecipitation analysis confirmed that OLA-NO2 replaced eNOS/Cav-1 with eNOS/Hsp90 interaction, resulting in increasing eNOS activity. OLA-NO2 also induced eNOS phosphorylation at Ser633 and Ser1177 and eNOS dephosphorylation at Ser113 and Thr495. In addition, OLA-NO2 induced phosphorylation of Akt and extracellular signal-regulated protein kinase (ERK1/2), which might contribute to eNOS activation. Collectively, these results substantiate a new functional role for nitrated fatty acid, demonstrating that OLA-NO2 exerts vascular protective effects by increasing NO bioavailability through eNOS phosphorylation/dephosphorylation and interaction with associated proteins such as Hsp90 and Cav-1.

Redox-dependent anti-inflammatory signaling actions of unsaturated fatty acids

Unsaturated fatty acids are metabolized to reactive products that can act as pro- or anti-inflammatory signaling mediators. Electrophilic fatty acid species, including nitro- and oxo-containing fatty acids, display salutary anti-inflammatory and metabolic actions. Electrophilicity can be conferred by both enzymatic and oxidative reactions, via the homolytic addition of nitrogen dioxide to a double bond or via the formation of α,β-unsaturated carbonyl and epoxide substituents. The endogenous formation of electrophilic fatty acids is significant and influenced by diet, metabolic, and inflammatory reactions. Transcriptional regulatory proteins and enzymes can sense the redox status of the surrounding environment upon electrophilic fatty acid adduction of functionally significant, nucleophilic cysteines. Through this covalent and often reversible posttranslational modification, gene expression and metabolic responses are induced. At low concentrations, the pleiotropic signaling actions that are regulated by these protein targets suggest that some classes of electrophilic lipids may be useful for treating metabolic and inflammatory diseases.

Toll-like receptor signaling pathways in cardiovascular diseases: challenges and opportunities

Toll-like receptors (TLRs), a family of surface molecules, are involved in innate immune responses. Recent studies indicated that TLRs play a critical role in inflammatory responses to exogenous and endogenous triggers. This article focuses on probable effects of TLRs in the morbidity of cardiovascular events, e.g., ischemic reperfusion (I/R) injury and atherosclerosis. TLR2 and TLR4 have been shown to have the most fundamental role in promoting cytokine production and subsequent inflammatory damages in these states. Blockade of these receptors may be beneficial in both preventing the occurrence and decreasing the complications in cardiovascular events. However, controversies exist on the certainty of this beneficial effect; therefore, additional studies are needed.

The Role of Sulfhydryl Reactivity of Small Molecules for the Activation of the KEAP1/NRF2 Pathway and the Heat Shock Response

The KEAP1/NRF2 pathway and the heat shock response are two essential cytoprotective mechanisms that allow adaptation and survival under conditions of oxidative, electrophilic, and thermal stress by regulating the expression of elaborate networks of genes with versatile protective functions. The two pathways are independently regulated by the transcription factor nuclear factor-erythroid 2 p45-related factor 2 (NRF2) and heat shock factor 1 (HSF1), respectively. The activity of these transcriptional master regulators increases during conditions of stress and also upon encounter of small molecules (inducers), both naturally occurring as well as synthetically produced. Inducers have a common chemical property: the ability to react with sulfhydryl groups. The protein targets of such sulfhydryl-reactive compounds are equipped with highly reactive cysteine residues, which serve as sensors for inducers. The initial cysteine-sensed signal is further relayed to affect the expression of large networks of genes, which in turn can ultimately influence complex cell fate decisions such as life and death. The paper summarizes the multiple lines of experimental evidence demonstrating that the reactivity with sulfhydryl groups is a major determinant of the mechanism of action of small molecule dual activators of the KEAP1/NRF2 pathway and the heat shock response.

Activation of stress signaling pathways by electrophilic oxidized and nitrated lipids

Unsaturated fatty acids are prone to radical reactions that occur in biological situations where extensive formation of reactive oxygen and nitrogen species (ROS and RNS) takes place. These reactions are frequent in inflammatory conditions such as atherosclerosis, and yield a variety of biologically active species, many of which are electrophilic in nature. Electrophilic lipid oxidation and nitration products can influence redox cell signaling via S-alkylation of protein thiols, and moderate exposure to these species evokes protective cell signaling responses through this mechanism. Herein, we review the stress signaling pathways elicited by electrophiles derived from unsaturated fatty acids, focusing on the Keap1-Nrf2 pathway, the heat shock response pathway (HSR), and the unfolded protein response pathway (UPR).

Acute rosiglitazone treatment is cardioprotective against ischemia-reperfusion injury by modulating AMPK, Akt, and JNK signaling in nondiabetic mice

Rosiglitazone (RGZ), a peroxisome proliferator-activated receptor (PPAR)-γ agonist, has been demonstrated to possess cardioprotective properties during ischemia-reperfusion. However, this notion remains controversial as recent evidence has suggested an increased risk in cardiac events associated with long-term use of RGZ in patients with type 2 diabetes. In this study, we tested the hypothesis that acute RGZ treatment is beneficial during I/R by modulating cardioprotective signaling pathways in a nondiabetic mouse model. RGZ (1 μg/g) was injected intravenously via the tail vein 5 min before reperfusion. Myocardial infarction was significantly reduced in mice treated with RGZ compared with vehicle controls (8.7% ± 1.1% vs. 20.2% ± 2.5%, P < 0.05). Moreover, isolated hearts were subjected to 20 min of global, no-flow ischemia in an ex vivo heart perfusion system. Postischemic recovery was significantly improved with RGZ treatment administered at the onset of reperfusion compared with vehicle ( P < 0.001). Immunoblot analysis data revealed that the levels of both phospho-AMP-activated protein kinase (Thr172) and phospho-Akt (Ser473) were significantly upregulated when RGZ was administered 5 min before reperfusion compared with vehicle. On the other hand, inflammatory signaling [phospho-JNK (Thr183/Tyr185)] was significantly downregulated as a result of RGZ treatment compared with vehicle ( P < 0.05). Intriguingly, pretreatment with the selective PPAR-γ inhibitor GW-9662 (1 μg/g iv) 10 min before reperfusion significantly attenuated these beneficial effects of RGZ on the ischemic heart. Taken together, acute treatment with RGZ can reduce ischemic injury in a nondiabetic mouse heart via modulation of AMP-activated protein kinase, Akt, and JNK signaling pathways, which is dependent on PPAR-γ activation.

The contribution of prostaglandins versus prostacyclin in ventricular remodeling during heart failure

Although the role of Cox-2 in the heart's response to physiologic stress remains controversial (i.e. expression in myocytes versus other resident myocardial cells) the ever expanding role of prostanoids in multiple models of heart failure cannot be denied. Due to the fact that prostanoids are metabolized rather quickly (half life of seconds to minutes) it is believed these signaling mediators act in a paracrine fashion at the site of production. Evidence to date is quite convincing that these bioactive lipid derivatives are involved in physiologic homeostatic regulation as well as beneficial and maladaptive ventricular remodeling in heart failure. Thus, this review will assess the direct contribution of each PG on remodeling in the left ventricle (e.g. hypertrophy, functional effects, and fibrosis).

15-Deoxy-Δ¹²,¹⁴-prostaglandin J₂, an electrophilic lipid mediator of anti-inflammatory and pro-resolving signaling

15-deoxy-Δ(12,14)-prostagandin J(2) (15d-PGJ2) is produced in the inflamed cells and tissues as a consequence of upregulation of cyclooxygenase-2 (COX-2). 15d-PGJ2 is known to be the endogenous ligand of peroxisome proliferator-activated receptor gamma (PPARγ) with multiple physiological properties. Though one of the terminal products of the COX-2-catalyzed reactions, this cyclopentenone prostaglandin exerts potent anti-inflammatory actions, in part, by antagonizing the activities of pro-inflammatory transcription factors, such as NF-κB, STAT3, and AP-1, while stimulating the anti-inflammatory transcription factor Nrf2. These effects are not necessarily dependent on its activation of PPARγ, but often involves direct interaction with the above signaling molecules and their regulators. The locally produced 15d-PGJ2 is also involved in the resolution of inflammatory responses. Thus, 15d-PGJ2, especially formed during the late phase of inflammation, might inhibit cytokine secretion and other events by antigen-presenting cells like dendritic cells or macrophages. 15d-PGJ2 can also affect the priming and effector functions of T lymphocytes and induce their apoptotic cell death. These represent a negative feedback explaining how once-initiated immunologic and inflammatory responses are switched off and terminated. In this context, 15d-PGJ2 and its synthetic derivatives have therapeutic potential for the treatment of inflammatory disorders.

Liver X receptor α activation with the synthetic ligand T0901317 reduces lung injury and inflammation after hemorrhage and resuscitation via inhibition of the nuclear factor κB pathway

Liver X receptor α (LXRα) is a nuclear transcription factor that regulates lipid metabolism. Recently, it has been shown that activation of LXRα with synthetic ligands has anti-inflammatory effects in atherosclerosis and chemical-induced dermatitis. We investigated the effect of the LXRα agonist, T0901317, on lung inflammation in a rodent model of hemorrhagic shock. Hemorrhagic shock was induced in male rats by withdrawing blood to a goal mean arterial blood pressure of 50 mmHg. Blood pressure was maintained at this level for 3 h, at which point rats were rapidly resuscitated with shed blood. Animals were then treated with T0901317 (50 mg · kg) or vehicle i.p. and sacrificed at 1, 2, and 3 h after resuscitation. Treatment with T0901317 significantly improved the cardiac and stroke volume indices as well as the heart rate of rats during the resuscitation period as compared with vehicle-treated rats. The T0901317-treated animals showed significant improvement in the plasma level of lactate, whereas base deficit and bicarbonate levels both trended toward improvement. The T0901317-treated animals also showed lower levels of plasma cytokines and chemokines monocyte chemoattractant protein 1, macrophage inflammatory protein 1α, TNF-α, KC, and IL-6. Lung injury and neutrophil infiltration were reduced by treatment with T0901317, as evaluated by histology and myeloperoxidase assay. At molecular analysis, treatment with T0901317 increased nuclear LXRα expression and DNA binding while also inhibiting activation of nuclear factor κB, a proinflammatory transcription factor, in the lung. Thus, our data suggest that LXRα is an important modulator of the inflammatory response and lung injury after severe hemorrhagic shock, likely through the inhibition of the nuclear factor κB pathway.

Optimal study design for pioglitazone in septic pediatric patients

The objective was to demonstrate the methodology and process of optimal sparse sampling pharmacokinetics (PK). This utilized a single daily dose of pioglitazone for pediatric patients with severe sepsis and septic shock based upon adult and minimal adolescent data. Pioglitazone pharmacokinetics were modeled using non-compartment analysis WinNonlin Pro (version 5.1) and population kinetics using NONMEM (version 7.1) with first order conditional estimation method (FOCE) with interaction. The initial model was generated from single- and multiple-dose pioglitazone PK data (15 mg, 30 mg, and 45 mg) in 36 adolescents with diabetes. PK models were simulated and overlaid upon original data to provide a comparison best described by a single compartment, first order model. The optimal design was based on the simulated oral administration of pioglitazone to three groups of pediatric patients, age 3.8 (2-6 years), weight 14.4 (7-28 kg); age 9.6 (6.1-11.9 years), weight 36.5 (28.1-48 kg) and age 15.5 (12-17 years,) weight 61.6 (48.1-80 kg). PFIM (version 3.2) was used to evaluate sample study size. Datasets were compiled using simulation for each dose (15, 30 and 45 mg) for the potential age/weight groups. A target dose of 15 mg daily in the youngest and middle groups was considered appropriate with area under the curve exposure levels (AUC) comparable to studies in adolescents. The final optimal design suggested time points of 0.5, 2, 6 and 21 h for 24 h dosing. This methodology provides a robust method of utilizing adult and limited adolescent data to simulate allometrically scaled, pediatric data sets that allow the optimal design of a pediatric trial. The pharmacokinetics of pioglitazone were described adequately and simulated data estimates were comparable to literature values. The optimal design provided clinically attainable sample times and windows.

New modalities in treating pneumococcal pneumonia

Despite the availability of effective antibiotics and intensive medical care, pneumococcal pneumonia is still associated with substantial mortality. Early diagnosis is becoming increasingly possible. This article reviews several adjunctive measures that might be instituted at or soon after admission in patients who are hospitalized for community-acquired pneumonia that is found to be due to Streptococcus pneumoniae. Available data favor the use of a macrolide together with a β-lactam antibiotic for treatment, based largely on immunomodulatory activity of macrolides. Two large subgroup analyses from a single major study suggest that activated protein C (eg, drotrecogin) should be considered for patients with severe sepsis, organ failure, and an Acute Physiology and Chronic Health Evaluation II score > 25 due to pneumococcal pneumonia. Statins exert an anti-inflammatory effect and several retrospective studies suggest that their use might ameliorate the adverse effects of pneumonia. Because inflammation elsewhere in the body is associated with inflammation in coronary arteries and because pneumococcal pneumonia has been shown to precipitate myocardial infarction, statins might be of further benefit by decreasing the likelihood of associated myocardial infarction. Aspirin, which inhibits platelet aggregation in inflamed coronary arteries, might also be considered for initial therapy. One reason that the association between myocardial infarction and pneumonia was not previously recognized is that aspirin was widely used in the past when people had acute febrile conditions. The literature on the benefits of corticosteroids in pneumonia is not convincing, and a particularly well-done, very recent study shows no benefit with corticosteroid use in patients with pneumococcal pneumonia, and perhaps even a worse outcome. No clinical data favor the use of platelet-activating factor antagonists.

Mediterranean diet and cardioprotection: the role of nitrite, polyunsaturated fatty acids, and polyphenols

The continually increasing rate of myocardial infarction (MI) in the Western world at least partly can be explained by a poor diet lacking in green vegetables, fruits, and fish and enriched in food that contains saturated fat. In contrast, a number of epidemiologic studies provide strong evidence highlighting the cardioprotective benefits of the Mediterranean diet enriched in green vegetables, fruits, fish, and grape wine. Regular consumption of these products leads to an accumulation of nitrate/nitrite/NO, polyunsaturated fatty acids (PUFA), and polyphenolic compounds, such as resveratrol, in the human body. Studies have confirmed that these constituents are bioactive exogenous mediators, which induce strong protection against MI. The aim of this review is to provide a critical, in-depth analysis of the cardioprotective pathways mediated by nitrite/NO, PUFA, and phenolic compounds of grape wines discovered in the recent years, including cross-talk between different mechanisms and compounds. Overall, these findings may facilitate the design and synthesis of novel therapeutic tools for the treatment of MI.

Activation of peroxisome-proliferator-activated receptors α and γ mediates remote ischemic preconditioning against myocardial infarction in vivo

Remote ischemic preconditioning (remote IPC) elicits a protective cardiac phenotype against myocardial ischemic injury. The remote stimulus has been hypothesized to act on major signaling pathways; however, its molecular targets remain largely undefined. We hypothesized that remote IPC exerts its effects by activating the peroxisome-proliferator-activated receptors (PPARs) α and γ, which have been previously implicated in cardioprotective signaling. Male New Zealand white rabbits (n = 78) were subjected to a 30-min coronary artery occlusion followed by three hours of reperfusion. Three cycles of remote IPC consisting of 10-min renal ischemia/reperfusion were performed. The animals either received the PPARα-antagonist GW6471 or the PPARγ-antagonist GW9662 alone or combined with remote IPC. Infarct size was determined gravimetrically. Tissue levels of 15d-prostaglandin J(2) (15d-PGJ(2)), as well as the PPAR DNA binding were measured using specific assays. Reverse transcriptase polymerase chain reaction was used to analyze changes in endothelial nitric oxide synthase or inducible nitric oxide synthase (iNOS) mRNA expression in relative quantity (RQ). Data are mean ± SD. As a result, remote IPC significantly reduced the myocardial infarct size (42.2 ± 4.9%* versus 61 ± 1.9%), accompanied by an increased PPAR DNA-binding (189.6 ± 19.8RLU* versus 44.4 ± 9RLU), increased iNOS expression (3.5 ± 1RQ* versus 1RQ), as well as 15d-PGJ(2) levels (179.7 ± 7.9 pg/mL* versus 127.9 ± 7.6 pg/mL). The protective response elicited by remote IPC, as well as the accompanying molecular changes were abolished by inhibiting PPARα (56.8 ± 4.7%; 61.1 ± 14.2RLU; and 1.91 ± 0.96RQ, respectively) or PPARγ (57.4 ± 3.3%; 52.7 ± 16.9RLU; and 1.54 ± 0.25RQ, respectively). (*Significantly different from control P < 0.05). In conclusion, the obtained results indicate that both PPARα and PPARγ play an essential role in remote IPC against myocardial infarction, impinging on the transcriptional control of iNOS expression.

Redox regulation of soluble epoxide hydrolase by 15-deoxy-delta-prostaglandin J2 controls coronary hypoxic vasodilation

RATIONALE

15-Deoxy-Δ-prostaglandin (15d-PG)J(2) is an electrophilic oxidant that dilates the coronary vasculature. This lipid can adduct to redox active protein thiols to induce oxidative posttranslational modifications that modulate protein and tissue function.

OBJECTIVE

To investigate the role of oxidative protein modifications in 15d-PGJ(2)-mediated coronary vasodilation and define the distal signaling pathways leading to enhanced perfusion.

METHODS AND RESULTS

Proteomic screening with biotinylated 15d-PGJ(2) identified novel vascular targets to which it adducts, most notably soluble epoxide hydrolase (sEH). 15d-PGJ(2) inhibited sEH by specifically adducting to a highly conserved thiol (Cys521) adjacent to the catalytic center of the hydrolase. Indeed a Cys521Ser sEH "redox-dead" mutant was resistant to 15d-PGJ(2)-induced hydrolase inhibition. 15d-PGJ(2) dilated coronary vessels and a role for hydrolase inhibition was supported by 2 structurally different sEH antagonists each independently inducing vasorelaxation. Furthermore, 15d-PGJ(2) and sEH antagonists also increased coronary effluent epoxyeicosatrienoic acids consistent with their vasodilatory actions. Indeed 14,15-EET alone induced relaxation and 15d-PGJ(2)-mediated vasodilation was blocked by the EET receptor antagonist 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE). Additionally, the coronary vasculature of sEH-null mice was basally dilated compared to wild-type controls and failed to vasodilate in response to 15d-PGJ(2). Coronary vasodilation to hypoxia in wild-types was accompanied by 15d-PGJ(2) adduction to and inhibition of sEH. Consistent with the importance of hydrolase inhibition, sEH-null mice failed to vasodilate during hypoxia.

CONCLUSION

This represents a new paradigm for the regulation of sEH by an endogenous lipid, which is integral to the fundamental physiological response of coronary hypoxic vasodilation.

Peroxisome-proliferator-activated receptor γ mediates the second window of anaesthetic-induced preconditioning

The second window of anaesthetic-induced preconditioning (APC) is afforded by the interplay of multiple signalling pathways, whereas a similar protective response is mediated by peroxisome-proliferator-activated receptor γ (PPARγ) agonists. However, a possible role of this nuclear receptor during APC has not been studied to date. We investigated the hypothesis that the second window of APC is mediated by the activation of PPARγ. New Zealand White rabbits (n = 48) were subjected to 30 min of coronary artery occlusion followed by 3 h of reperfusion. The animals received desflurane (1.0 minimal alveolar concentration), the PPARγ antagonist GW9662, as well as the combined application of both, respectively, 24 h prior to coronary artery occlusion. Infarct size was determined gravimetrically; tissue levels of 15-deoxy-(12,14)-prostaglandin J(2) (15d-PGJ(2)) and nitrite/nitrate (NO(x)), as well as PPAR DNA binding were measured using specific assays. Data are presented as means ± s.e.m. Desflurane led to a reduced myocardial infarct size (41.7 ± 2.5 versus 61.8 ± 2.8%, P < 0.05), accompanied by significantly increased PPAR DNA binding (289.9 ± 33 versus 102.9 ± 18 relative light units, P < 0.05), as well as elevated tissue levels of 15d-PGJ(2) (224.4 ± 10.2 versus 116.9 ± 14.2 pg ml(-1), P < 0.05) and NO(x) (14.9 ± 0.7 versus 5.4 ± 0.7 μm, P < 0.05). Pharmacological inhibition of PPARγ abolished these protective effects, resetting the infarct size (56.5 ± 2.9%), as well as PPAR DNA-binding activity (91.2 ± 31 relative light units) and NO(x) tissue levels (5.9 ± 0.9 μm) back to control levels. Desflurane governs a second window of APC by increasing the production of 15d-PGJ(2), subsequently activating PPARγ, resulting in a diminished myocardial infarct size by increasing the downstream availability of NO.

Milk fat globule-EGF factor VIII in sepsis and ischemia-reperfusion injury

Sepsis and ischemia-reperfusion (I/R) injury are among the leading causes of death in critically ill patients at the surgical intensive care unit setting. Both conditions are marked by the excessive inflammatory response which leads to a lethal disease complex such as acute lung injury, systemic inflammatory response syndrome and multiple organ dysfunction syndrome. Despite the advances in the understanding of the pathophysiology of those conditions, very little progress has been made toward therapeutic interventions. One of the key aspects of these conditions is the accumulation of apoptotic cells that have the potential to release toxic and proinflammatory contents due to secondary necrosis without appropriate clearance by phagocytes. Along with the prevention of apoptosis, that is reported to be beneficial in sepsis and I/R injury, thwarting the development of secondary necrosis through the active removal of apoptotic cells via phagocytosis may offer a novel therapy. Milk fat globule-EGF factor VIII (MFG-E8), which is mainly produced by macrophages and dendritic cells, is an opsonin for apoptotic cells and acts as a bridging protein between apoptotic cells and phagocytes. Recently, we have shown that MFG-E8 expression is decreased in experimental sepsis and I/R injury models. Exogenous administration of MFG-E8 attenuated the inflammatory response as well as tissue injury and mortality through the promotion of phagocytosis of apoptotic cells. In this review, we describe novel information available about the involvement of MFG-E8 in the pathophysiology of sepsis and I/R injury, and the therapeutic potential of exogenous MFG-E8 treatment for those conditions.

Albumin-binding and tumor vasculature determine the antitumor effect of 15-deoxy-Delta-(12,14)-prostaglandin-J(2) in vivo

15-Deoxy-Delta(12,14)-prostaglandin-J(2) (15d-PGJ(2)), a peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, induces cell death in tumor cells in vitro; however, no study showed its in vivo effect on tumors. Here, we report that 15d-PGJ(2) shows antitumor effects in vivo in mice. However, its effects correlate with tumor uptake of albumin, to which it reversibly binds. 15d-PGJ(2) induces cell death in B16F10 melanoma and C26 colon carcinoma cells in vitro. These effects were not elicited through PPARgamma-dependent pathways because an irreversible PPARgamma antagonist GW9662 did not inhibit these effects. Caspase- and nuclear factor kappaB- (NF-kappaB) dependent pathways were found to be involved as determined with caspase-3/7 fluorescent assay and NF-kappaB containing plasmid transfection assay, respectively. Noticeably, 15d-PGJ(2) had significantly stronger effects in C26 cells compared with B16 cells in all assays. However, in vivo, there was no effect on C26 tumors, yet it significantly inhibited the B16 tumor growth in mice by 75%. We found that 15d-PGJ(2) rapidly bound to albumin and in vivo albumin greatly distributed to B16 tumors compared with C26 tumors, shown with gamma-camera imaging and immunohistochemical staining. Albumin accumulation can be attributed to the large blood vessel diameter in B16 tumors and an enhanced permeability and retention effect. These findings suggest that 15d-PGJ(2) can be an effective therapeutic agent for cancer, although its effects seem to be limited to the tumors allowing albumin penetration.

Peroxisome proliferator-activated receptor-gamma ligands 15-deoxy-delta(12,14)-prostaglandin J2 and pioglitazone inhibit hydroxyl peroxide-induced TNF-alpha and lipopolysaccharide-induced CXC chemokine expression in neonatal rat cardiac myocytes

Ligands for peroxisome proliferator-activated receptor gamma (PPAR-gamma) such as prostaglandin metabolite 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2) or thiazolidinedione pioglitazone have been identified as a new class of anti-inflammatory compounds with possible clinical applications. Reactive oxygen species play an important role in the generation of cellular damage by induction of proinflammatory cytokines and chemokines during myocardial I/R. These events were preceded by activation of the transcription factors nuclear factor (NF)-kappaB pathway. It has been suggested that myocardium overproduces TNF-alpha after I/R, and locally produced TNF-alpha is sufficient to cause severe impairment of cardiac function. LPS-induced CXC chemokine (LIX) is a rodent chemokine with potent neutrophil-chemotactic activity. Based on this concept, we examined the effects of 15d-PGJ2 and pioglitazone on oxidative stress-induced TNF-alpha and LIX expression in neonatal rat cardiac myocytes. Pretreatment of myocytes with 15d-PGJ2 or pioglitazone decreased hydrogen peroxide-induced TNF-alpha and LIX production (mRNA and protein) in a concentration-dependent manner. The beneficial effects of both ligands were associated with reduction of hydrogen peroxide-induced NF-kappaB activation. Treatment with 15d-PGJ2, but not pioglitazone, caused dose-dependent activation of heat shock factor 1, which could render cells unresponsive to stimulation of NF-kappaB. The cytoprotection afforded by pioglitazone was attenuated by the PPAR-gamma antagonist GW9662, which failed to affect the beneficial effects afforded by 15d-PGJ2. Taken together, these results demonstrate that treatment with these chemically distinct ligands of PPAR-gamma results in diverse anti-inflammatory mechanisms.

Transduction of redox signaling by electrophile-protein reactions

Over the last 50 years, the posttranslational modification (PTM) of proteins has emerged as a central mechanism for cells to regulate metabolism, growth, differentiation, cell-cell interactions, and immune responses. By influencing protein structure and function, PTM leads to a multiplication of proteome diversity. Redox-dependent PTMs, mediated by environmental and endogenously generated reactive species, induce cell signaling responses and can have toxic effects in organisms. PTMs induced by the electrophilic by-products of redox reactions most frequently occur at protein thiols; other nucleophilic amino acids serve as less favorable targets. Advances in mass spectrometry and affinity-chemistry strategies have improved the detection of electrophile-induced protein modifications both in vitro and in vivo and have revealed a high degree of amino acid and protein selectivity of electrophilic PTM. The identification of biological targets of electrophiles has motivated further study of the functional impact of various PTM reactions on specific signaling pathways and how this might affect organisms.

Toll-like receptors in ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injuries are implicated in a large array of pathological conditions such as myocardial infarction, cerebral stroke, and hepatic, renal, and intestinal ischemia, as well as following cardiovascular and transplant surgeries. The hallmark of these pathologies is excessive inflammation. Toll-like receptors (TLRs) are recognized as one of the main contributors to pathogen-induced inflammation and, more recently, injury-induced inflammation. Endogenous ligands such as low-molecular hyaluronic acid, fibronectin, heat shock protein 70, and heparin sulfate were all found to be cleaved in the inflamed tissue and to activate TLR2 and TLR4, initiating an inflammatory response even in the absence of pathogens and infiltrating immune cells. In this review, we discuss the contribution of TLR activation in hepatic, renal, cerebral, intestinal, and myocardial I/R injuries. A greater understanding of the role of TLRs in I/R injuries may aid in the development of specific TLR-targeted therapeutics to treat these conditions.

Lung injury after hemorrhage is age dependent: role of peroxisome proliferator-activated receptor gamma

OBJECTIVE

The incidence of multiple organ failure in pediatric trauma victims is lower than in the adult population. However, the molecular mechanisms are not yet defined. We investigated whether the pathophysiologic characteristics of hemorrhage-induced lung injury may be age dependent and may be regulated by the peroxisome proliferator-activated receptor gamma (PPARgamma).

DESIGN

Prospective, laboratory investigation that used an established rodent model of hemorrhagic shock.

SETTING

University hospital laboratory.

SUBJECTS

Young (n = 67; 3-5 months old) and mature (n = 66; 11-13 months old) male rats.

INTERVENTIONS

Hemorrhagic shock was induced in young and mature rats by withdrawing blood to a mean arterial blood pressure of 50 mm Hg. After 3 hours, rats were rapidly resuscitated by infusing the shed blood and killed 3 hours thereafter.

MEASUREMENTS AND MAIN RESULTS

In young rats, lung injury was characterized by accumulation of red cells and neutrophils at the end of the resuscitation period; on Western blot analysis, lung expression of intercellular adhesion molecule-1 was increased. In contrast, the severity of lung injury was more pronounced in mature rats. Lung myeloperoxidase activity and expression of constitutive and inducible intercellular adhesion molecule-1 was significantly higher in mature rats compared with young rats. Mature rats also had higher plasma levels of cytokines and chemokines compared with young rats. This heightened inflammation was associated with higher degree of activation of nuclear factor-kappaB and down-regulation of PPARgamma and heat shock factor-1 in the lung of mature rats compared with young rats. Treatment with the PPARgamma ligand, the cyclopentenone prostaglandin 15-deoxy-Delta-prostaglandin J2, ameliorated lung injury in young, but not in mature animals.

CONCLUSIONS

Lung injury after severe hemorrhage is age dependent and may be secondary to a diverse regulation of PPARgamma.

Significance of peroxisome proliferator-activated receptors in the cardiovascular system in health and disease

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear transcription factors that belong to the nuclear receptor superfamily. Three isoforms of PPAR have been identified, alpha, delta and gamma, which play distinct roles in the regulation of key metabolic processes, such as glucose and lipid redistribution. PPARalpha is expressed predominantly in the liver, kidney and heart, and is primarily involved in fatty acid oxidation. PPARgamma is mainly associated with adipose tissue, where it controls adipocyte differentiation and insulin sensitivity. PPARdelta is abundantly and ubiquitously expressed, but as yet its function has not been clearly defined. Activators of PPARalpha (fibrates) and gamma (thiazolidinediones) have been used clinically for a number of years in the treatment of hyperlipidaemia and to improve insulin sensitivity in diabetes. More recently, PPAR activation has been found to confer additional benefits on endothelial function, inflammation and thrombosis, suggesting that PPAR agonists may be good candidates for the treatment of cardiovascular disease. In this regard, it has been demonstrated that PPAR activators are capable of reducing blood pressure and attenuating the development of atherosclerosis and cardiac hypertrophy. This review will provide a detailed discussion of the current understanding of basic PPAR physiology, with particular reference to the cardiovascular system. It will also examine the evidence supporting the involvement of the different PPAR isoforms in cardiovascular disease and discuss the current and potential future clinical applications of PPAR activators.

Ciglitazone ameliorates lung inflammation by modulating the inhibitor kappaB protein kinase/nuclear factor-kappaB pathway after hemorrhagic shock

OBJECTIVE

Peroxisome proliferator-activated receptor-gamma is a ligand-activated transcription factor. Ciglitazone, a peroxisome proliferator-activated receptor-gamma ligand, has been shown to provide beneficial effects in experimental models of sepsis and ischemia/reperfusion injury. We investigated the effects of ciglitazone on lung inflammation after severe hemorrhage.

DESIGN

Prospective, laboratory study, rodent model of hemorrhagic shock.

SETTING

University hospital laboratory.

SUBJECTS

Male rats.

INTERVENTIONS

Hemorrhagic shock was induced by withdrawing blood to a mean arterial pressure of 50 mm Hg. At 3 hrs after hemorrhage, rats were rapidly resuscitated by returning their shed blood. At the time of resuscitation and every hour thereafter, animals received ciglitazone (10 mg/kg) or vehicle intraperitoneally. Heart rate and mean arterial pressure were measured throughout the experiment. Plasma and lung tissue were collected for analysis up to 3 hrs after resuscitation.

MEASUREMENTS AND MAIN RESULTS

Ciglitazone treatment ameliorated mean arterial pressure, reduced lung injury, significantly blunted lung neutrophil infiltration, and lowered plasma interleukin-6, interleukin-10, and monocyte chemoattractant protein-1 levels. In a time course analysis, vehicle-treated rats had a significant increase in nuclear factor-kappaB DNA binding, which was preceded by increased inhibitor kappaB protein kinase activity and inhibitor kappaB alpha degradation in the lung. Treatment with ciglitazone significantly reduced inhibitor kappaB protein kinase activity and inhibitor kappaB alpha degradation and completely inhibited nuclear factor-kappaB DNA binding. This reduction of inhibitor kappaB protein kinase activity afforded by ciglitazone appeared to be a consequence of a physical interaction between peroxisome proliferator-activated receptor-gamma and increased inhibitor kappaB protein kinase.

CONCLUSION

Ciglitazone ameliorates the inflammatory response and may reduce lung injury after hemorrhagic shock. These protective effects appear to be mediated through inhibition of the inhibitor kappaB protein kinase/nuclear factor-kappaB pathway.

15-deoxy-delta12,14-prostaglandin J2 attenuates endothelial-monocyte interaction: implication for inflammatory diseases

BACKGROUND

The Infiltration of leukocytes across the brain endothelium is a hallmark of various neuroinflammatory disorders. Under inflammatory conditions, there is increased expression of specific cell adhesion molecules (CAMs) on activated vascular endothelial cells which increases the adhesion and infiltration of leukocytes. TNFalpha is one of the major proinflammatory cytokines that causes endothelial dysfunction by various mechanisms including activation of transcription factor NF-kappaB, a key transcription factor that regulates expression of CAMs. Peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the nuclear hormone superfamily of ligand-activated transcriptional factors. 15-deoxy-delta 12, 14-prostaglandin J2 (15d-PGJ2) is a well recognized natural ligand of PPARgamma and possesses anti-inflammatory properties both in vitro and in vivo. This study aims to elucidate the mechanism of 15-PGJ2 on the adhesion of mononuclear cells to activated endothelial cells.

METHODS

To delineate the signaling pathway of 15d-PGJ2 mediated effects, we employed an in vitro adhesion assay model of endothelial-monocyte interaction. Expression of CAMs was examined using flow cytometry and real time PCR techniques. To define the mechanism of 15d-PGJ2, we explored the role of NF-kappaB by EMSA (Electrophoretic Mobility Shift Assay) gels, NF-kappaB reporter and p65-transcriptional activities by transient transfection in the brain-derived endothelial cell line (bEND.3).

RESULTS

Using an in vitro adhesion assay model, we demonstrate that 15d-PGJ2 inhibits TNFalpha induced monocyte adhesion to endothelial cells, which is mediated by downregulation of endothelial cell adhesion molecules in a PPARgamma independent manner. 15d-PGJ2 modulated the adhesion process by inhibiting the TNFalpha induced IKK-NF-kappaB pathway as evident from EMSA, NF-kappaB reporter and p65 mediated transcriptional activity results in bEND.3 cells.

CONCLUSION

These findings suggest that 15d-PGJ2 inhibits inflammation at multiple steps and thus is a potential therapeutic target for various inflammatory diseases.

Oxidized glycerophosphocholines as biologically active mediators for ultraviolet radiation-mediated effects

Ultraviolet light radiation (UVR) has profound effects upon human skin. Yet, the exact targets for UVR are unclear. Inasmuch as UVR is a known pro-oxidative stressor, one potential target for UVR could be oxidatively modified glycerophosphocholines (GPC). Importantly, recent studies demonstrate that these oxidized GPCs (ox-GPC) are potent agonists for the platelet-activating factor receptor and peroxisome proliferator-activated receptor gamma. This review discusses these new biologically active lipids and their down-stream receptor targets that provide a unique system of biosensors for detecting and responding to UVR photo-oxidation.